powerpc: ppc4xx: remove lwmon5 support

This has not been converted to Generic Board, so should be removed.
(See doc/README.generic-board for details.)

Remove CONFIG_LWMON5 references.
(Also, remove undefined CONFIG_WD_MAX_RATE while I am here.)

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Stefan Roese <sr@denx.de>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index 87e2b35..2697451 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,7 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+lwmon5           powerpc     ppc4xx         -           -           Stefan Roese <sr@denx.de>
 csb272/csb472    powerpc     ppc4xx         -           -           Tolunay Orkun <torkun@nextio.com>
 alpr             powerpc     ppc4xx         -           -           Stefan Roese <sr@denx.de>
 cam_enc_4xx      arm         arm926ejs      8d775763    2015-08-20  Heiko Schocher <hs@denx.de>